In recent years, telecommunications service providers have developed a variety of special service features that may prevent an incoming call to a customer's telephone or mobile station. Such features, for example, include various call blocking services and parental control. With such services, the network will block an incoming call at least under certain circumstances, e.g. at certain times of day, unless the identification of the calling party or station meets certain criteria (is recognized as that of an acceptable caller) or the caller enters an acceptable password or personal identification number (PIN). Prepaid services also may prevent an incoming call when the balance on the prepaid account is insufficient to pay for any costs that may be associated with the called party answering the call.
Modern telecommunications networks also support emergency calling with a variety of related features to help insure that public safety personnel receive each emergency call and have all data that may help them to respond quickly in an appropriate manner. In the US, emergency calls are typically made by dialing 911 on the landline telephone or mobile station. The network routes such a call to a public safety answering point (PSAP) and provides ancillary data, such as caller location information. These types of services have proven very effective.
Hence, when a subscriber places a call to well known emergency numbers such as 911, the network currently recognizes this as an emergency call and takes special action to route the call to the appropriate PSAP where emergency call takers can assist the subscriber. The network also facilitates the PSAP personnel to retrieve the physical location of the subscriber and also the phone number of the subscriber (i.e. callback number). In the US, the FCC (Federal Communication Commission) has various mandates which cover what information needs to be provided to PSAPs for various telecommunication services. In cases wherein the call gets disconnected abruptly, the PSAP personnel try to reach the subscriber again by calling the callback number that is provided by the network. It is imperative that the callback option is available.
When the PSAP calls back the station that initiated the emergency call, there is currently nothing special in the call related signaling or otherwise to indicate to the network that this call is originating from an emergency service responder or that this call is related to an emergency. As there is nothing special about the emergency callback it gets treated as a regular incoming call by the network. If the subscriber has a restriction of some type associated with the callback number that blocks incoming calls, the network may not deliver the call from the PSAP personnel to the caller involved in the emergency, based on the applicable subscriber or network restriction. Failure to deliver the callback may hamper efforts of emergency personnel to determine the nature of the emergency and/or provide the appropriate response.
It may help to consider a few more examples of the services that may block the emergency callback, in somewhat more detail, before discussing prior efforts to address this conflict. There are various services that a subscriber may activate or restrictions that the network enforces that can prevent the emergency callback from reaching the subscriber. One example is a Selective Call Acceptance service. This service allows a subscriber to create a list of numbers associated with permitted calling parties' stations or lines. Only those callers having their numbers on that list will be able to ring onto the subscriber's line or mobile station. When someone whose number is not on the subscriber's list tries to call (e.g. the PSAP personnel trying to reach the subscriber after interruption of an emergency call), they will be notified that the subscriber is not accepting calls from them at this time.
Another service example is a call intercept service. This service enables a subscriber to apply a “Do Not Disturb” capability so that incoming calls are not permitted to reach the subscriber's number (incoming calls to the subscriber telephone line or mobile station) unless the call is from a previously authorized list of numbers, or if the calling party has a special Personal Identification Number (PIN). When the service is active, it may not be possible for the PSAP call taker to complete a callback to the calling party because of the incoming call restriction.
Other flavors of the above service exist (e.g. incoming call screening, etc.) in wireline, wireless and VoIP networks that would inadvertently result in restricting the callback from the PSAP. Callback from the PSAP could also be restricted as a side-effect from services like prepaid, usage control, parental monitoring etc. For example, if the subscriber associated with the telephone or mobile station that made the 911 call had only X minutes of usage for placing incoming and outgoing voice calls and if those X minutes get consumed prior to or during the emergency call, the network may permit the outbound 911 call but block the in-bound callback from the PSAP personnel.
There have been prior suggestions to address these issues regarding conflicts between various types of call blocking and the need to permit callbacks from the PSAP. For example, all the lines in the PSAPs that could be used to make a callback after a 911 call could be identified. These numbers can be placed into a database associated with the service that will recognize a call from one of the numbers as a PSAP callback and disable the incoming call restriction allowing the call to complete to the telephone or mobile station that made the 911 call. Alternatively, for services that can be bypassed by a subscriber entered PIN an administrative PIN can be designated as an override PIN to be used by the PSAPs to disable the incoming call restriction.
These prior approaches have not proved entirely satisfactory. Entry of the PSAP numbers for use as known numbers from which incoming calls are permitted involves developing and maintaining a potentially large database, because each PSAP may have a large amount of different numbers associated with it that may appear in the signaling for outbound calls such as those associated with 911 callback attempts. There are more than 6000 PSAPs in the nation, therefore maintaining an accurate database of outgoing PSAP lines is not really practical. The PIN solution is applicable only to services that can be overridden by a PIN, which is not necessarily true of all services or other restrictions that might otherwise block a callback from a PSAP. The PIN solution, for example, may not be enough to allow a callback if the restriction relates to a balance on a prepaid account of the party involved in the emergency. Also, the PIN approach requires knowledge and use of the PIN in response to network prompts. If required to be done manually, this introduces opportunities for human error. Even if automated, the PIN entry introduces additional delay in the callback operation. Also, service specific override PINs could become known to unauthorized persons and could be misused.
Hence, a need exits for a more effective technique to prevent incoming call restrictions from blocking a callback after an emergency call.